Switching power converters (SPCs) are used to regulate the input voltage to a load. Often times, voltages are initially not suitable for a particular load (e.g., high AC) and must be downscaled (i.e., to a lower voltage) and/or converted (i.e., AC to DC rectified voltage) before applying to the load. In general, conventional SPC systems adequately provide voltage regulation to a load, however, there are drawbacks.
Traditional converter control methods are typically locked into one or two modes of operation (e.g., Pulse Width Modulation (PWM), constant ON time variable frequency, constant ON or OFF time and variable frequency, simultaneous phases ON, and simultaneous phases OFF). Depending on the particular load demands, utilizing one mode over another may improve control of the output voltage. Thus, a single operational mode converter typically cannot efficiently accommodate power delivery to complex or dynamic load requirements.
Slope compensation is often utilized in current mode power converters to stabilize the current loop. Conventional current mode controlled converters operating above 50% duty cycle need a compensating ramp signal superimposed on a current sense signal, which is used as a control parameter, to avoid open loop instability, subharmonic oscillations, and noise sensitivity. SPCs using current mode control typically include a pair of complex poles at half the regulator switching frequency and external ramp or slope compensation is added into the current loop in order to control the Q of these poles. In general, additional components are required to generate the fixed slope compensation in discrete applications.
It is common to couple more than one load to a power regulation system. In these multi-load/multi-output configurations, SPCs have traditionally required a separate controller or transformer with post regulators for each of the outputs. Each control unit requires compensating elements and support components which substantially increases the parts count for the converter. Additionally, in multi-output systems it is often desirable to include time synchronization to produce multi-phased outputs. These complex systems require precise management and control which, in general, the traditional purely analog converter systems cannot adequately manage. While transformers have shown some success in multi-output power conversion, these systems again typically require multiple controllers.
With the advent of increasingly complex power regulation topologies, more precise control of the switching elements (i.e. synchronous rectifiers) and better control methods have been attempted. Digital techniques for power converter control, specifically in multiphase designs, can improve precision and reduce the system's parts count. Digital control can also be upgraded for different applications of the same power system, e.g., for programmable feedback control.
Microprocessor loads vary greatly in current and generally require a high di/dt load transient current. For these applications, the power conversion system must be able to sense the current or voltage droop in order to correct for the load demand. Current sensing of the load is difficult and typically requires bulky, lossy and inaccurate methods. Voltage sensing has the disadvantage of lagging the current in the load. Delays in both methods can lead to inadequate response of the SPC.
Accordingly, an improved power regulation system is needed. In particular, a highly phased power regulation system having multi-mode capabilities over one or more loads is desired. More particularly, a versatile and adaptable power conversion and regulation system having an improved control feature is desired.